Electrolytic processing of metallic substrates

ABSTRACT

Provided herein are methods and systems for electrolytic processing of metallic substrates, such as aluminum alloys. The disclosure provides methods of making an anodized substrate by anodizing a metallic substrate in an electrolyte solution comprising phosphoric acid. In particular, the disclosure describes various conditions for anodizing the metallic substrate, including temperature, acid concentration, and voltage. The disclosure also provides systems for carrying out described methods.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and filing benefit of U.S.provisional patent application Ser. No. 62/988,857, filed Mar. 12, 2020,which is incorporated herein by reference in its entirety.

FIELD

The present disclosure generally relates to electrolytic processing ofmetallic substrates, such as aluminum alloys, and to systems forcarrying out such processing. More specifically, the present disclosurerelates to anodizing metallic substrates.

BACKGROUND

Certain metal products, such as aluminum alloys, can benefit from havingan anodized surface. These benefits include durability, color stability,ease of maintenance, aesthetics, health and safety, and low cost.However, it is difficult to anodize aluminum alloy coils having ananodized film that meets flexibility, durability and/or surfacecharacteristics requirements for downstream processing, includingjoining of aluminum alloy products. Furthermore, conventional methodsfor anodizing are time-consuming and require high expense, which reducesthe overall efficiency of production processes. In addition,conventional anodizing methods require multiple baths, typically of highconcentrations of acid, which contribute to the inefficiency whileexposing operators to unsafe conditions. Thus, conventional methods ofanodizing are ineffective.

SUMMARY

Covered embodiments of the invention are defined by the claims, not thissummary. This summary is a high-level overview of various aspects of theinvention and introduces some of the concepts that are further describedin the Detailed Description section below. This summary is not intendedto identify key or essential features of the claimed subject matter, noris it intended to be used in isolation to determine the scope of theclaimed subject matter. The subject matter should be understood byreference to appropriate portions of the entire specification, any orall drawings, and each claim.

In one aspect, the present disclosure describes a method of making ananodized substrate, the method comprising: providing a metallicsubstrate; optionally, cleaning a surface of the metallic substrate;anodizing the surface of the metallic substrate in an electrolytesolution at a temperature from 60° C. to 100° C. to form an anodizedfilm layer, wherein the electrolyte solution comprises from 0.01 M to 1M of an electrolyte; and optionally, drying the surface of the metallicsubstrate. In some cases, the electrolyte is an inorganic acid selectedfrom the group consisting of phosphoric acid, nitric acid, sulfuricacid, phosphonic acid, and combinations thereof. In some cases, theelectrolyte solution comprises from 0.05 M to 0.5 M electrolyte, andoptionally the electrolyte is phosphoric acid. In some cases, theanodizing comprises applying a direct current (DC) having a voltage from±15 VDC to ±25 VDC and/or applying an alternating current (AC) having avoltage from ±15 VAC to ±25 VAC to the electrolyte solution for at least5 seconds. In some cases, the anodizing comprises applying the AC for atleast 5 seconds before and/or after applying the DC for at least 15seconds. In some cases, cleaning the surface of the metal substratecomprises rinsing the surface of the metallic substrate with a solvent.In some cases, the metallic substrate is not etched before anodizing. Insome cases, the metallic substrate comprises an aluminum alloy.

In another aspect, the present disclosure describes a method of makingan anodized substrate, the method comprising: providing a metallicsubstrate; optionally, cleaning a surface of the metallic substrate;anodizing the surface of the metallic substrate in an electrolytesolution by applying a direct current (DC) having a voltage from ±15 VDCto ±25 VDC and/or applying an alternating current (AC) having a voltagefrom ±15 VAC to ±25 VAC to the electrolyte solution for at least 5seconds, wherein the electrolyte solution comprises from 0.01 M to 1 Mof an electrolyte; and optionally, drying the surface of the metallicsubstrate. In some cases, the electrolyte is an inorganic acid selectedfrom the group consisting of phosphoric acid, nitric acid, sulfuricacid, phosphonic acid, and combinations thereof. In some cases, theelectrolyte solution comprises from 0.05 M to 0.5 M electrolyte, andoptionally the electrolyte is phosphoric acid. In some cases, theanodizing comprises applying the AC for at least 5 seconds before and/orapplying the DC for at least 15 seconds. In some cases, the electrolytesolution is heated to a temperature from 60° C. to 100° C. In somecases, cleaning the surface of the metal substrate comprises rinsing thesurface of the metallic substrate with a solvent. In some cases, themetallic substrate is not etched before anodizing. In some cases, themetallic substrate comprises an aluminum alloy.

In another aspect, the present disclosure describes a system foranodizing a metallic substrate, the system comprising: an electrolyticcell having a metallic cathode; an electrolyte solution source forproviding an electrolyte solution comprising from 0.01 M to 1 M of anelectrolyte; a support for suspending the metallic substrate in thebath; and a power supply from providing a direct current (DC) and/oralternating current (AC) to the electrolytic cell and through theelectrolyte solution. In some cases, the electrolyte solution comprisesfrom 0.05 M to 0.5 M electrolyte, and optionally the electrolyte isphosphoric acid. In some cases, the electrolyte solution sourcecomprises a tank having an agitator. In some cases, the electrolyticcell further comprises one or more compound electrodes.

DETAILED DESCRIPTION

Described herein are methods and systems for making an anodizedsubstrate from a metallic substrate, such as an aluminum alloysubstrate. The resultant anodized substrates can be used, for example,to produce anodized substrate (e.g., anodized aluminum alloy) productsthat have superior surface qualities and minimized surface defects ascompared to products prepared from metallic substrates without ananodized film layer as described herein.

The methods described herein provide a more efficient means of forming athin anodized film layer on one or more surfaces of a metallicsubstrate. Particularly, the methods described herein successfullyanodize the metallic substrate without the need for a separate step ofetching the metallic substrate (e.g., acid etching and/or electrolyticetching). Furthermore, the methods described herein successfully anodizethe metallic substrate using one chemical bath, eliminating the need formultiple chemical baths. These new anodizing methods allow for shorteroperation time, improved environmental health and safety, and reducedcost. Furthermore, the anodized substrate produced by the methodsdescribed herein exhibit excellent physical properties, such as bonddurability, and is suitable for coil-to-coil lines as well as batchprocessing.

Definitions and Descriptions

As used herein, the terms “invention,” “the invention,” “this invention”and “the present invention” are intended to refer broadly to all of thesubject matter of this patent application and the claims below.Statements containing these terms should be understood not to limit thesubject matter described herein or to limit the meaning or scope of thepatent claims below.

In this description, reference is made to alloys identified by aluminumindustry designations, such as “series” or “7xxx.” For an understandingof the number designation system most commonly used in naming andidentifying aluminum and its alloys, see “International AlloyDesignations and Chemical Composition Limits for Wrought Aluminum andWrought Aluminum Alloys” or “Registration Record of Aluminum AssociationAlloy Designations and Chemical Compositions Limits for Aluminum Alloysin the Form of Castings and Ingot,” both published by The AluminumAssociation.

Aluminum alloys are described herein in terms of their elementalcomposition in weight percentage (wt. %) based on the total weight ofthe alloy. In certain examples of each alloy, the remainder is aluminum,with a maximum wt. % of 0.15% for the sum of the impurities.

As used herein, “bond durability” refers to an ability of a bondingagent bonding two products together to withstand cycled mechanicalstress after exposure to environmental conditions that initiate failureof the bonding agent. Bond durability is characterized in terms of thenumber of mechanical stress cycles applied to the bonded products, whilethe bonded products are exposed to the environmental conditions, untilthe bond fails.

As used herein, terms such as “cast metal product,” “cast product,”“cast aluminum alloy product,” and the like are interchangeable andrefer to a product produced by direct chill casting (including directchill co-casting) or semi-continuous casting, continuous casting(including, for example, by use of a twin belt caster, a twin rollcaster, a twin block caster, or any other continuous caster),electromagnetic casting, hot top casting, or any other casting method.

As used herein, a “continuous coil” or an “aluminum alloy continuouscoil” refers to an aluminum alloy subjected to a continuous processingmethod on a continuous line without breaks in time or sequence (i.e.,the aluminum alloy is not subjected to batch processing).

As used herein, a “coil-to-coil” line or “coil-to-coil processing”refers to a continuous processing method on a continuous line wherebythe alloy, e.g., aluminum alloy, processed in the method is fed into theprocessing from a coil, uncoiled during the processing, and re-coiledafter completing the processing.

Reference is made in this application to alloy condition or temper. Foran understanding of the alloy temper descriptions most commonly used,see “American National Standards (ANSI) H35 on Alloy and TemperDesignation Systems.” An F condition or temper refers to an aluminumalloy as fabricated. An O condition or temper refers to an aluminumalloy after annealing. A TI condition or temper refers to an aluminumalloy cooled from hot working and naturally aged (e.g., at roomtemperature). A T2 condition or temper refers to an aluminum alloycooled from hot working, cold worked, and naturally aged. A T3 conditionor temper refers to an aluminum alloy solution heat treated, coldworked, and naturally aged. A T4 condition or temper refers to analuminum alloy solution heat treated and naturally aged. A T5 conditionor temper refers to an aluminum alloy cooled from hot working andartificially aged (at elevated temperatures). A T6 condition or temperrefers to an aluminum alloy solution heat treated and artificially aged.A T7 condition or temper refers to an aluminum alloy solution heattreated and artificially overaged. A T8x condition or temper refers toan aluminum alloy solution heat treated, cold worked, and artificiallyaged. A T9 condition or temper refers to an aluminum alloy solution heattreated, artificially aged, and cold worked.

As used herein, the meaning of “a,” “an,” or “the” includes singular andplural references unless the context clearly dictates otherwise.

As used herein, the meaning of “room temperature” can include atemperature of from about 15° C. to about 30° C., for example about 15°C., about 16° C., about 17° C., about 18° C., about 19° C., about 20°C., about 21° C., about 22° C., about 23° C., about 24° C., about 25°C., about 26° C., about 27° C., about 28° C., about 29° C., or about 30°C.,

All ranges disclosed herein are to be understood to encompass any andall subranges subsumed therein. For example, a stated range of “1 to 10”should be considered to include any and all subranges between (andinclusive of) the minimum value of 1 and the maximum value of 10; thatis, all subranges beginning with a minimum value of 1 or more, e.g. 1 to6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10.

Metallic Substrate

As noted, the present disclosure provides methods and systems for makingan anodized substrate. More specifically, the methods described hereinproduce a thin anodized film layer on the surface of a metallicsubstrate. The composition of the metallic substrate on which theanodized film layer is formed is not particularly limited. The methodsdescribed herein are particularly well suited, but not limited, toanodizing an aluminum alloy. The anodized film layer can be applied, forexample, to any suitable aluminum alloy, such as a continuous coil of analuminum alloy. Suitable aluminum alloys include, for example, 1xxxseries aluminum alloys. 2xxx series aluminum alloys, 3xxx seriesaluminum alloys, 4xxx series aluminum alloys, 5xxx series aluminumalloys, 6xxx series aluminum alloys, 7xxx series aluminum alloys, and8xxx series aluminum alloys.

By way of non-limiting example, exemplary 1xxx series aluminum alloysfor use as the metallic substrate can include AA1100, AA1100A, AA1200,AA1200A, AA1300, AA1110, AA1120, AA1230, AA1230A, AA1235, AA1435,AA1145, AA1345, AA1445, AA1150, AA1350, AA1350A, AA1450, AA1370, AA1275,AA1185, AA1285, AA1385, AA1188, AA1190, AA1290, AA1193, AA1198, orAA1199. In some cases, the aluminum alloy is at least 99.9% purealuminum (e.g., at least 99,91%, at least 99.92%, at least 99.93%, atleast 99.94%, at least 99.95%, at least 99.96%, at least 99.97%, atleast 99,98%, or at least 99.99% pure aluminum).

Non limiting exemplary 2xxx series aluminum alloys for use as themetallic substrate can include AA2001, AA2002, AA2004, AA2005, AA2006,AA2007, AA2007A, AA2007B, AA2008, AA2009, AA2010, AA2011, AA2011A,AA2111, AA2111A, AA2111B, AA2012, AA2013, AA2014, AA2014A, AA2214,AA2015, AA2016, AA2017, AA2017A, AA2117, AA2018, AA2218, AA2618,AA2618A, AA2219, AA2319, AA2419, AA2519, AA2021, AA2022, AA2023, AA2024,AA2024A, AA2124, AA2224, AA2224A, AA2324, AA2424, AA2524, AA2624,AA2724, AA2824, AA2025, AA2026, AA2027, AA2028, AA2028A, AA2028B,AA2028C, AA2029, AA2030, AA2031, AA2032, AA2034, AA2036, AA2037, AA2038,AA2039, AA2139, AA2040, AA2041, AA2044, AA2045, AA2050, AA2055, AA2056,AA2060, AA2065, AA2070, AA2076, AA2090, AA2091, AA2094, AA2095, AA2195,AA2295, AA2196, AA2296, AA2097,AA2197, AA2297, AA2397, AA2098, AA2198,AA2099, and AA2199.

Non-limiting exemplary 3xxx series aluminum alloys for use as themetallic substrate can include AA3002, AA3102, AA3003, AA3103, AA3103A,AA3103B, AA3203, AA3403, AA3004, AA3004A, AA3104, AA3204, AA3304,AA3005, AA3005A, AA3105, AA3105A, AA3105B, AA3007, AA3107, AA3207,AA3207A, AA3307, AA3009, AA3010, AA3110, AA3011, AA3012, AA3012A,AA3013, AA3014, AA3015, AA3016, AA3017, AA3019, AA3020, AA3021, AA3025,AA3026, AA3030, AA3130, or AA3065.

Non-limiting exemplary 4xxx series aluminum alloys for use as themetallic substrate can include AA4004, AA4104, AA4006, AA4007, AA4008,AA4009, AA4010, AA4013, AA4014, AA4015, AA4015A, AA4115, AA4016, AA4017,AA4018, AA4019, AA4020, AA4021, AA4020, AA4032, AA4043, AA4043A, AA4143,AA4343, AA4643, AA4943, AA4044, AA4045, AA4145, AA4145A, AA4046, AA4047,AA4047A, and AA4147.

Non-limiting exemplary 5xxx series aluminum alloys for use as themetallic substrate can include AA5182, AA5183, AA5005, AA5005A, AA5205,AA5305, AA5505, AA5605, AA5006, AA5106, AA5010, AA5110, AA5110A, AA5210,AA5310, AA5016, AA5017, AA5018, AA5018A, AA5019, AA5019A, AA5119,AA5119A, AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028, AA5040,AA5140, AA5041, AA5042, AA5043, AA5049, AA5149, AA5249, AA5349, AA5449,AA5449A, AA5050, AA5050A, AA5050C, AA5150, AA5051, AA5051A, AA5151,AA5251, AA5251A, AA5351A, AA5451A, AA5052, AA5252, AA5352, AA5154,AA5154A, AA5154B, AA5154C, AA5254, AA5354, AA5454, AA5554, AA5654,AA5654A, AA5754, AA5854, AA5954, AA5056, AA5356, AA5356A, AA5456,AA5456A, AA5456B, AA5556, AA5556A, AA5556B, AA5556C, AA5257, AA5457,AA5557, AA5657, AA5058, AA5059, AA5070, AA5180, AA5180A, AA5082, AA5182,AA5083, AA5183, AA5183A, AA5283, AA5283A, AA5283B, AA5383, AA5483,AA5086, AA5186, AA5087, AA5187, or AA5088.

Non-limiting exemplary 6xxx series aluminum alloys for use as themetallic substrate can include AA6101, AA6101A, AA6101B, AA6201,AA6201A, AA6401, AA6501, AA6002, AA6003, AA6103, AA6005, AA6005A,AA6005, B, AA6005C, AA6105, AA6205, AA6305, AA6006, AA6106, AA6206,AA6306, AA6008, AA6009, AA6010, AA6110, AA6110A, AA6011, AA6111, AA6012,AA6012A, AA6013, AA6113, AA6014, AA6015, AA6016, AA6016A, AA6116,AA6018, AA6019, AA6020, AA6021, AA6022, AA6023, AA6024, AA6025, AA6026,AA6027, AA6028, AA6031, AA6032, AA6033, AA6040, AA6041, AA6042, AA6043,AA6151, AA6351, AA6351A, AA6451, AA6951, AA6053, AA6055, AA6056, AA6156,AA6060, AA6160, AA6260, AA6360, AA6460, AA6460B, AA6560, AA6660, AA6061,AA6061A, AA6261, AA6361, AA6162, AA6262, AA6262A, AA6063, AA6063A,AA6463, AA6463A, AA6763, A6963, AA6064, AA6064A, AA6065, AA6066, AA6068,AA6069, AA6070, AA6081, AA6181, AA6181A, AA6082, AA6082A, AA6182,AA6091, or AA6092.

Non-limiting exemplary 7xxx series aluminum alloys for use as themetallic substrate can include AA7011, AA7019, AA7020, AA7021, AA7039,AA7072, AA7075, AA7085, AA7108, AA7108A, AA7015, AA7017, AA7018,AA7019A, AA7024, AA7025, AA7028, AA7030, AA7031, AA7033, AA7035,AA7035A, AA7046, AA7046A, AA7003, AA7004, AA7005, AA7009, AA7010,AA7011, AA7012, AA7014, AA7016, AA7116, AA7122, AA7023, AA7026, AA7029,AA7129, AA7229, AA7032, AA7033, AA7034, AA7036, AA7136, AA7037, AA7040,AA7140, AA7041, AA7049, AA7049A, AA7149, AA7204, AA7249, AA7349, AA7449,AA7050, AA7050A, AA7150, AA7250, AA7055, AA7155, AA7255, AA7056, AA7060,AA7064, AA7065, AA7068, AA7168, AA7175, AA7475, AA7076, AA7178, AA7278,AA7278A, AA7081, AA7181, AA7185, AA7090, AA7093, AA7095, or AA7099.

Non-limiting exemplary 8xxx series aluminum alloys for use as themetallic substrate cane include AA8005, AA8006, AA8007, AA8008, AA8010,AA8011, AA8011A, AA8111, AA8211, AA8112, AA8014, AA8015, AA8016, AA8017,AA8018, AA8019, AA8021, AA8021A, AA8021B, AA8022, AA8023, AA8024,AA8025, AA8026, AA8030, AA8130, AA8040, AA8050, AA8150, AA8076, AA8076A,AA8176, AA8077, AA8177, AA8079, AA8090, AA8091, and AA8093.

While aluminum alloy products are described throughout the disclosure,the methods and products apply to any metallic substrate. In someembodiments, the metallic substrate is aluminum, an aluminum alloy,magnesium, a magnesium-based material, titanium, a titanium-basedmaterial, copper, a copper-based material, steel, a steel-basedmaterial, bronze, a bronze-based material, brass, a brass-basedmaterial, a composite, a sheet used in composites, or any other suitablemetal or combination of materials. The product may include monolithicmaterials, as well as non-monolithic materials such as roll-bondedmaterials, clad materials, composite materials, or various othermaterials. In some examples, the metal article is a metal coil, a metalstrip, a metal plate, a metal sheet, a metal billet, a metal ingot, orthe like.

The metallic substrate can be prepared from an alloy of any suitabletemper. In certain examples, the alloys can be used in F, O, T3, T4, T6,or T8x tempers. The alloys can be produced by direct chill casting(including direct chill co-casting) or semi-continuous casting,continuous casting (including, for example, by use of a twin beltcaster, a twin roll caster, a block caster, or any other continuouscaster), electromagnetic casting, hot top casting, or any other castingmethod.

Anodized Film Layer

As described above, an anodized film layer is formed by the methodsdescribed herein on a surface of the metallic substrate. The anodizedfilm layer includes a barrier layer, which is composed of aluminum oxide(e.g., nonporous aluminum oxide). The barrier layer can be up to about25 nm in thickness. In some cases, the barrier layer can be from about 1nm to about 25 nm, from about 5 nm to about 25 nm, from about 10 nm toabout 20 nm, or from about 12 nm to about 17 nm in thickness. By way ofexample, the barrier layer can be about 1 nm, about 2 nm, about 3 nm,about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm,about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, about15 nm, about 16 nm, about 17 nm, about 18 nm, about 19 nm, about 20 nm,about 21 nm, about 22 nm, about 23 nm, about 24 nm, or about 25 nm inthickness, or anywhere in between.

In some cases, the anodized film layer may include a filament layer. Thefilament layer is composed of aluminum oxide (e.g., porous aluminumoxide) and may be include a series of column-like, porous structures.The characteristics of the filament layer (e.g., the characteristics ofthe column-like, porous structures) may be controlled by anodizingparameters and conditions (e.g., composition of the electrolytesolution). The filament layer can be up to about 75 nm in thickness. Insome cases, the filament layer can be from about 5 nm to about 800 nm,from about 10 nm to about 750 nm, from about 25 nm to about 700 nm, orfrom about 45 nm to about 650 nm in thickness. By way of example, thefilament layer can be about 5 nm, about 25 nm, about 50 nm, about 75 nm,about 150 nm, about 200 nm, about 300 nm, about 350 nm, about 400 nm,about 450 nm, about 550 nm, about 600 nm, about 650 nm, about 700 nm,about 750 nm, or about 800 in thickness, or anywhere in between.

In some cases, the anodized film layer may include a barrier layer ofany thickness described above and a filament layer of any thicknessdescribed above. In some cases, the anodized film layer includes abarrier layer of about 10 nm, about 15 nm, about 20 nm or about 25 nmand a filament layer of about 650 nm, about 700 nm, about 750 nm, orabout 800 nm. By way of example, the anodized film layer may include abarrier layer of about 10 nm and a filament layer of about 650 nm, abarrier layer of about 15 nm and a filament layer of about 700 nm, abarrier layer of about 20 nm and a filament layer of about 750 nm, or abarrier layer of about 25 nm and a filament layer of about 800 nm.

The thickness of the anodized film layer, including the barrier layer orthe barrier layer and the filament layer, can range from about 1 nm toabout 1000 nm. In some cases, the anodized film layer is less than about1000 nm in thickness, e.g., less than about 900 nm, less than about 800nm, less than about 700 nm, less than about 600 nm, less than about 500nm, less than about 400 nm, less than about 300 nm, less than about 200nm, or less than about 100 nm. For example, the anodized film layer canbe from about 5 nm to about 1000 nm, from about 10 nm to about 900 nm,from about 20 nm to about 800 nm, or from about 30 nm to about 700 nm inthickness. In some examples, the anodized film layer can be about 1 nm,5 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm,about 35 nm, about 40 nm, about 45 nm, about 50 nm, about 55 nm, about60 nm, about 65 nm, about 70 nm, about 75 nm, about 80 nm, about 85 nm,about 90 nm, about 95 nm, about 100 nm, about 150 nm, about 250 nm,about 300 nm, about 400 nm, about 500 nm, about 600, about 700, about750 nm, about 800 nm, about 825 nm, about 850 nm, about 900 nm, about950 nm, or about 1000 nm in thickness, or anywhere in between.

Methods of Making an Anodized Substrate

The present disclosure provides methods of making an anodized substrate.The methods of anodizing the metallic substrate, as described herein,include an optional preparation step, an anodizing step, and an optionaldrying step. As noted above, the methods described herein do not includea separate step of etching the metallic substrate (e.g., acid etchingand/or electrolytic etching). Furthermore, the methods can be carriedout using one chemical bath, eliminating the need for the multiplechemical baths required in conventional anodizing methods. As a result,these new anodizing methods allow for shorter operation time, improvedenvironmental health and safety, and reduced cost.

The metallic substrate as described herein can be subjected toprocessing techniques prior to anodizing to provide the metallicsubstrate in a form suitable for anodizing. In some cases, for example,processing techniques may be employed to provide a metallic substrate inthe form of a continuous coil, including, for example, casting,homogenizing, hot rolling, warm rolling, cold rolling, solution heattreating, annealing, aging (including natural aging and/or artificialaging), any suitable processing techniques, and/or any combinationsthereof. Accordingly, anodizing may be performed as a step subsequent tothe processing techniques described above to provide the continuouscoils or other metallic substrates. For example, the anodizing can becarried out after processing the metal substrate in a cold rolling mill,an annealing furnace, a continuous annealing and solution heat treating(CASH) line, or any suitable final processing equipment. Said anotherway, the anodizing described herein may occur between a penultimatemetal processing step and the coiling of the metal substrate. Thus, themetallic substrate can be processed into a metal product and can beanodized immediately after processing without coiling the metal product(e.g., to provide the continuous coil). In some cases, the metallicsubstrates described herein can be anodized after coiling. The metallicsubstrates can be stored (e.g., to naturally age the metallicsubstrates) or artificially aged before anodizing. In such instances,the metallic substrates (e.g., the stored metallic substrates or theartificially aged metallic substrates) can be uncoiled and fed into thesystems described herein for anodizing.

The methods may be employed in a continuous coil process, e.g., wherethe metallic substrate is composed of one or more continuous coilsspliced or joined together. Line speeds for the continuous coil processare variable and can be in the range of about 1 meter per minute (mpm)to about 350 mpm. For example, the line speed can be about 1 mpm, about2 mpm, about 3 mpm, about 4 mpm, about 5 mpm, about 6 mpm, about 7 mpm,about 8 mpm, about 9 mpm, about 10 mpm, about 15 mpm, about 20 mpm,about 25 mpm, about 30 mpm, about 35 mpm, about 40 mpm, about 45 mpm,about 50 mpm, about 55 mpm, about 60 mpm, about 65 mpm, about 70 mpm,about 75 mpm, about 80 mpm, about 85 mpm, about 90 mpm, about 95 mpm,about 100 mpm, about 105 mpm, about 110 mpm, about 115 mpm, about 120mpm, about 125 mpm, about 130 mpm, about 135 mpm, about 140 mpm, about145 mpm, about 150 mpm, about 155 mpm, about 160 mpm, about 165 mpm,about 170 mpm, about 175 mpm, about 180 mpm, about 185 mpm, about 190mpm, about 195 mpm, about 200 mpm, about 205 mpm, about 210 mpm, about215 mpm, about 220 mpm, about 225 mpm, about 230 mpm, about 235 mpm,about 240 mpm, about 245 mpm, about 250 mpm, about 255 mpm, about 260mpm, about 265 mpm, about 270 mpm, about 275 mpm, about 280 mpm, about285 mpm, about 290 mpm, about 295 mpm, about 300 mpm, about 305 mpm,about 310 mpm, about 315 mpm, about 320 mpm, about 325 mpm, about 330mpm, about 335 mpm, about 340 mpm, about 345 mpm, or about 350 mpm, oranywhere in between.

Preparation

Before anodizing, the metallic substrate may undergo a preparation step.The preparation step may prepare the metallic substrate for anodizing.For example, the optional preparation step may include cleaning one ormore surfaces of the metallic substrate. The optional cleaning stepremoves residual oils, or loosely adhering oxides, from the surface ofthe metallic substrate.

Optionally, cleaning can be performed using a solvent (e.g., an aqueousor organic solvent) as a cleaner. Suitable cleaners can include, forexample, water (e.g., distilled water, demineralized water, or deionizedwater), an acid (e.g., sulfuric acid, hydrofluoric acid, nitric acid,phosphoric acid, boric acid, or citric acid), a caustic (e.g., sodiumhydroxide, potassium hydroxide, calcium oxide, calcium carbonate,calcium hydroxide, lithium hydroxide, magnesium hydroxide, ammoniumhydroxide), hexane, ethanol, acetone, or any combination thereof. Thecleaner may further comprise one or more additives added to the solvent.In some non-limiting examples, the cleaner can be sprayed onto one ormore surfaces of the continuous coil. In some aspects, the cleaning stepcan be performed by spraying water and/or a cleaning solution onto oneor more surfaces of the metallic substrate at a suitable pressure, suchas a pressure of from about 2 bar to about 4 bar. For example, thesurfaces of the metallic substrate can be sprayed at a pressure of about2 bar, 2.1 bar, 2.2 bar, 2.3 bar, 2.4 bar, 2.5 bar, 2.6 bar, 2.7 bar,2.8 bar, 2.9 bar, 3 bar, 3.1 bar, 3.2 bar, 3.3 bar, 3.4 bar, 3.5 bar,3.6 bar, 3.7 bar, 3.8 bar, 3.9 bar, 4 bar, or anywhere in between.Additionally, the cleaner can be heated prior to application to one ormore surfaces of the metallic substrate. In some non-limiting examples,the cleaner can be heated to a temperature of from about 85° C. to about100° C. For example, the cleaner can be heated to a temperature of about85° C., 86° C., 87° C., 88° C., 89° C., 90° C., 91° C., 92° C., 93° C.,94° C., 95° C., 96° C., 97° C., 98° C., 99° C. 100° C., or anywhere inbetween.

As noted, the cleaning step is optional. In some cases, the metallicsubstrate is not subjected to the cleaning step before anodizing. Insome cases, the metallic substrate is only subjected to the cleaningstep if residual oils are visible on one or more surfaces of themetallic substrate.

The optional preparation step preferably does not include a preparatoryetching step. In conventional methods of anodizing a metallic substrate,the metallic substrate is etched, e.g., by an alkaline solution and/oran electrolyte solution, prior to anodizing to further clean the surfaceand/or to prepare one or more surfaces of the metal substrate foranodizing. The methods described herein effectively form an anodizedfilm layer on a surface of the metallic substrate without the need for apreparatory etching step. Because the methods described herein do notrequire the preparatory etching step, the methods described hereinrequire fewer chemical baths than conventional anodizing methods. Inmost instances, a single chemical bath is required for the anodizingmethod. This increases the overall efficiency of the processing byreducing both time and expense of carrying out the method. Furthermore,by reducing the need for harsh alkaline and/or acidic baths, the methodsdescribed herein provide for improved environmental health and safety.

Anodizing

In the methods described herein, the metallic substrate is subjected toan anodizing step, whereby an anodized film layer is formed, e.g., onone or more surfaces of the metallic substrate, to form one or more thinanodized film surfaces. In some cases, the thin anodized film surface isa final product. In certain examples, the thin anodized film surface isa substrate for subsequent coatings (e.g., one or more pretreatmentsincluding an adhesion promoter, a corrosion inhibitor, a coupling agent,any suitable pretreatment solution, or any combination thereof). Theanodizing is accomplished by contacting the surface of the metallicsubstrate with an electrolyte solution, passing the metallic substratethrough the active zone of the one or more electrolytic cells, andflowing an electric current through the electrolyte solution, therebycreating an electrical circuit.

The electrolyte solution is composed of an aqueous solution of anelectrolyte, e.g., an electrolyte dissolved and/or diluted in water.Suitable electrolytes include, for example, inorganic acids such asphosphoric acid, nitric acid, sulfuric acid, phosphonic acid, andcombinations of these. Other exemplary electrolytes include aqueoussolutions of sodium nitrate, sodium chloride, potassium nitrate,magnesium chloride, sodium acetate, copper sulfate, potassium chloride,magnesium nitrate, potassium nitrate, calcium chloride, lithiumchloride, sodium carbonate, potassium carbonate, calcium carbonate,sodium bicarbonate, ammonium acetate, silver nitrate, ferric chloride,ammonium pentaborate, boric acid, citric acid, ammonium adipate,ammonium phosphate monobasic, or any combination thereof, among others.

The electrolyte solution includes the electrolyte in an amount from 0.01M to 1 M. In some non-limiting examples, the electrolyte solutionincludes the electrolyte in an amount from about 0.01 M to about 1 M,e.g., from 0.01 M to 0.8 M, from 0.01 M to 0.6 M, from 0.01 M to 0.5 M,from 0.01 M to 0.4 M, from 0.01 M to 0.2 M, from 0.02 M to 1 M, from0.02 M to 0.8 M, from 0.02 M to 0.5 M, from 0.02 M to 0.6 M, from 0.02.M to 0.4 M, from 0.02 M to 0.2 M, from 0.4 M to 1 M, from 0.4 M to 0.8M, from 0.04 M to 0.6 M, from 0.04 M to 0.5 M, from 0.04 M to 0.4 M,from 0.04 M to 0.2 M, from 0.05 M to 1 M, from 0.05 M to 0.8 M, from0.05 M to 0.5 M, from 0.05 M to 0.6 M, from 0.05 M to 0.4 M, from 0.05 Mto 0.2 M, from 0.06 M to 1 M, from 0.06 M to 0.8 M, from 0.06 M to 0.6M, from 0.06 M to 0.5 M, from 0.06 M to 0.4 M, from 0.06 M to 0.2 M,from 0.08 M to 1 M, from 0.08 M to 0.8 M, from 0.08 M to 0.6 M, from0.08 M to 0.5 M from 0.08 M to 0.4 M, or from 0.08 M to 0.2 M. In termsof lower limits, the electrolyte solution may include the electrolyte inan amount greater than 0.01 M, e.g., greater than 0.02 M, greater than0.04 M, greater than 0.05 M, greater than 0.06 M, or greater than 0.08M. In terms of upper limits, the electrolyte solution may include theelectrolyte in an amount less than 1 M, e.g., less than 0.8 M, less than0.6 M, less than 0.5 M, less than 0.4 M, or less than 0.2 M. Forexample, the electrolyte solution may include about 0.08 M electrolyte,about 0.09 M electrolyte, about 0.1 M electrolyte, about 0.12 Melectrolyte, about 0.15 M electrolyte, or about 0.18 M electrolyte.

Each of the above ranges of concentrations of electrolyte in theelectrolyte solution is applicable for any of the suitable electrolytedescribed above. For example, the electrolyte solution may comprise aninorganic acid, such as phosphoric acid, nitric acid, sulfuric acid,phosphonic acid, or combinations thereof, at any of the concentrationsdisclosed above for the electrolyte in the electrolyte solution.

The electrolyte solution of the methods described herein includes alower concentration of electrolyte than electrolyte solutions ofconventional anodizing methods. In conventional anodizing methods,electrolyte solutions having an electrolyte concentration of at leastabout 2 M are typically used. The methods described herein effectivelyform an anodized film layer on a surface of the metallic substratewithout the need for high concentration electrolyte solutions. Thisfurther increases the overall efficiency of the processing by reducingthe expense of carrying out the method. Furthermore, becauseconventional anodizing methods typically utilize highly concentratedacid solution, the methods described herein provide for improvedenvironmental health and safety.

The means of passing the metallic substrate through the active zone ofone or more electrolytic cells and flowing an electric current throughthe electrolyte solution is not particularly limited. In some cases, ametallic cathode, e.g., composed of stainless steel, may be used to forman electric circuit with the metallic substrate. In some cases, themetallic cathode may be a contact roll (e.g., a contact roll electrode).The one or more electrolytic cells may also include one or more counterelectrodes. For example, an electrolytic cell may comprise a firstcounter electrode disposed parallel to a first surface of the metallicsubstrate and a second counter electrode disposed parallel to a secondsurface of the metallic substrate.

Power can be applied to the metallic cathode and/or the one or morecounter electrodes, thus forming an alternating current (AC) circuit ora direct current (DC) circuit. The current flow in the electrolytesolution releases oxygen ions, which can migrate to a surface ofmetallic substrate and form a metallic oxide on the surface. Forexample, the metallic substrate may be composed of an aluminum alloy,and the oxygen ions released due to the flow of AC or DC may combinewith aluminum on the surface of the metallic substrate to form alumina(Al₂O₃). Applying power to the counter electrode(s) can ensureanodization occurs at an interface between the electrolyte and thesurface of the metallic substrate.

In some cases, power is applied to form an AC circuit. The AC powerapplied to the metallic cathode and/or the one or more counterelectrodes can range from about ±10 Volts AC (VAC) to about ±35 VAC,e.g., from about ±15 Volts AC (VAC) to about ±35 VAC, from about ±18 VACto about ±34 VAC, from about ±20 VAC to about ±32 VAC, or from about ±22VAC to about ±30 VAC. In terms of lower limits, the AC power applied maybe greater than ±15 VAC, e.g., greater than ±18 VAC, greater than ±20VAC, or greater than ±22 VAC. In terms of upper limits, the AC powerapplied may be less than ±35 VAC, e.g., less than ±34 VAC, less than ±32VAC, or less than ±30 VAC. For example, the AC power applied may beabout ±22 VAC, about ±24 VAC, about ±26 VAC, or about ±28 VAC.

The metallic substrate can be anodized by applying the AC for a settime, e.g., by exposing the metallic substrate to the AC for a set time.In some cases, the AC is applied for at least 5 seconds, e.g., at least6 seconds, at least 7 seconds, at least 8 seconds, or at least 9seconds. In terms of upper limits, the AC may be applied for less than 5minutes, e.g., less than 2 minutes, less than 1 minute, less than 30seconds, or less than 20 seconds. In terms of ranges, the AC may beapplied for from 5 seconds to 5 minutes, e.g., from 6 seconds to 2minutes, from 7 seconds to 1 minute, from 8 seconds to 30 seconds, orfrom 9 seconds to 20 seconds. For example, the metallic substrate may beexposed to the energized electrolyte solution for about 7 seconds, about8 seconds, about 9 seconds, about 10 seconds, about 11 seconds, about 12seconds, about 13 seconds, about 14 seconds, about 15 seconds, about 16seconds, or about 17 seconds.

The AC circuit formed may be any waveform, e.g., a sinusoidal waveform,a rectangular waveform, a sawtooth waveform, a triangular waveform, or asquare waveform.

In some cases, power is applied to form a DC circuit. The DC powerapplied to the metallic cathode and/or the one or more counterelectrodes can range from about ±10 Volts DC (VDC) to about ±35 VDC,e.g., from about ±15 Volts DC (VDC) to about ±35 VDC, from about ±18 VDCto about ±34 VDC, from about ±20 VDC to about ±32 VDC, or from about ±22VDC to about ±30 VDC. In terms of lower limits, the DC power applied maybe greater than ±15 VDC, e.g., greater than ±18 VDC, greater than ±20VDC, or greater than ±22 VDC. In terms of upper limits, the DC powerapplied may be less than ±35 VDC, e.g., less than ±34 VDC, less than ±32VDC, or less than ±30 VDC. For example, the DC power applied may beabout ±22 VDC, about ±24 VDC, about ±26 VDC, or about ±28 VDC.

The metallic substrate can be anodized by applying the DC for a settime, e.g., by exposing the metallic substrate to the DC for a set time.In some cases, the DC is applied for at least 5 seconds, e.g., at least7 seconds, at least 10 seconds, at least 12 seconds, or at least 15seconds. In terms of upper limits, the DC may be applied for less than10 minutes, e.g., less than 5 minutes, less than 2 minutes, less than 1minute, or less than 30 seconds. In terms of ranges, the DC may beapplied for from 5 seconds to 10 minutes, e.g., from 7 seconds to 5minutes, from 10 seconds to 2 minutes, from 12 seconds to 1 minute, orfrom 15 seconds to 30 seconds. For example, the metallic substrate maybe exposed to the energized electrolyte solution for about 10 seconds,about 12 seconds, about 14 seconds, about 16 seconds, about 18 seconds,about 20 seconds, about 22 seconds, about 24 seconds, about 26 seconds,about 28 seconds, or about 30 seconds.

In some cases, a surface of the metallic substrate is anodized byapplying an AC alone or by applying a DC alone. In some cases, a surfaceof the metallic substrate is anodized by applying both AC power and DCpower, e.g., in sequence. Said another way, anodizing a surface of themetallic substrate may include applying the AC and subsequently applyingthe DC and/or applying the DC and subsequently applying the AC. Forexample, the anodizing may include applying the AC for at least 5seconds before and/or after applying the DC for at least 5 seconds,e.g., applying the AC for about 5 seconds before and/or after applyingthe DC for about 5 seconds, applying the AC for about 5 seconds beforeand/or after applying the DC for about 10 seconds, applying the AC forabout 5 seconds before and/or after applying the DC for about 15seconds, applying the AC for about 5 seconds before and/or afterapplying the DC for about 20 seconds, applying the AC for about 8seconds before and/or after applying the DC for about 5 seconds,applying the AC for about 8 seconds before and/or after applying the DCfor about 10 seconds, applying the AC for about 8 seconds before and/orafter applying the DC for about 15 seconds, applying the AC for about 8seconds before and/or after applying the DC for about 20 seconds,applying the AC for about 10 seconds before and/or after applying the DCfor about 5 seconds, applying the AC for about 10 seconds before and/orafter applying the DC for about 10 seconds, applying the AC for about 10seconds before and/or after applying the DC for about 15 seconds,applying the AC for about 10 seconds before and/or after applying the DCfor about 20 seconds, applying the AC for about 12 seconds before and/orafter applying the DC for about 5 seconds, applying the AC for about 12seconds before and/or after applying the DC for about 10 seconds,applying the AC for about 12 seconds before and/or after applying the DCfor about 15 seconds, or applying the AC for about 12 seconds beforeand/or after applying the DC for about 20 seconds

In some cases, during the anodizing step, the metallic substrate, e.g.,a continuous coil or a portion of the metallic substrate (such as asurface of the metallic substrate), may be immersed in a bath of theelectrolyte solution. Optionally, the electrolyte solution can becirculated to ensure a fresh solution is continuously exposed to thealuminum alloy continuous coil surfaces.

The temperature of the electrolyte solution bath can be from about 60°C. to about 100° C., e.g., from about 65° C. to about 98° C., from about70° C. to about 95° C., from about 75° C. to about 92° C., from about70° C. to about 90° C., or from about 75° C. to about 90° C. In terms oflower limits, the temperature of the electrolyte solution bath may begreater than 60° C., e.g., greater than 65° C., greater than 70° C., orgreater than 75° C. In terms of upper limits, the temperature of theelectrolyte solution bath may be less than 100° C., e.g., less than 98°C., less than 95° C., less than 92° C., or less than 90° C. For example,the temperature of the electrolyte bath can be about 60° C., about 61°C., about 62° C., about 63° C., about 64° C., about 65° C., about 66°C., about 67° C., about 68° C., about 69° C., about 70° C., about 71°C., about 72° C., about 73° C., about 74° C., about 75° C., about 76°C., about 77° C., about 78° C., about 79° C., about 80° C., about 81°C., about 82° C., about 83° C., about 84° C., about 85° C., about 86°C., about 87° C., about 88° C., about 89° C., about 90° C., about 91°C., about 92° C., about 93° C., about 94° C., about 95° C., about 96°C., about 97° C., about 98° C., about 99° C., or about 100° C.

The concentration of components in the electrolyte solution can bemeasured according to techniques as known to those of skill in the art,such as by a titration procedure for free and total acid or byinductively coupled plasma (ICP). For example, the aluminum content canbe measured by ICP and controlled to be within a certain range. In someexamples, the aluminum content is controlled to be less than about 10.0g/L. For example, the aluminum content can be less than about 9.5 g/L,less than about 9.0 g/L, less than about 8.5 g/L, less than about 8.0g/L, less than about 7.5 g/L, less than about 7.0 g/L, less than about6.5 g/L, less than about 6.0 g/L, less than about 5.5 g/L, less thanabout 5.0 g/L, less than about 4.5 g/L, less than about 4.0 g/L, lessthan about 3.5 g/L, less than about 3.0 g/L, less than about 2.5 g/L,less than about 2.0 g/L, less than about 1.5 g/L, less than about 1.0g/L, less than about 0.5 g/L, less than about 0.4 g/L, less than about0.3 g/L, less than about 0.2 g/L, or less than about 0.1 g/L.

In some cases, during the anodizing step, the electrolyte solution maybe sprayed onto a surface of the metallic substrate. In some aspects,the electrolyte solution may be sprayed onto the surface of the metallicsubstrate at a pressure of from about 2 bar to about 4 bar. For example,the electrolyte solution can be sprayed onto the surface at a pressureof about 2 bar, 2.1 bar, 2.2 bar, 2.3 bar, 2.4 bar, 2.5 bar, 2.6 bar,2.7 bar, 2.8 bar, 2.9 bar, 3 bar, 3.1 bar, 3.2 bar, 3.3 bar, 3.4 bar,3.5 bar, 3.6 bar, 3.7 bar, 3.8 bar, 3.9 bar, 4 bar, or anywhere inbetween. Additionally, the electrolyte solution can be heated prior toapplication onto the surface of the metallic substrate. In somenon-limiting examples, the electrolyte solution can be heated to atemperature of from about 60° C. to about 100° C., e.g., from about 65°C. to about 98° C., from about 70° C. to about 95° C., from about 75° C.to about 92° C., from about 70° C. to about 90° C., or from about 75° C.to about 90° C. In terms of lower limits, the electrolyte solution maybe heated to a temperature greater than 60° C., e.g., greater than 65°C., greater than 70° C., or greater than 75° C. In terms of upperlimits, the electrolyte solution may be heated to a temperature lessthan about 100° C., e.g., less than about 98° C., less than about 95°C., less than about 92° C., or less than about 90° C. For example, theelectrolyte solution may be heated to a temperature of 60° C., 61° C.,62° C., 63° C., 64° C., 65° C., 66° C., 67° C., 68° C., 69° C., 70° C.,71° C., 72° C., 73° C., 74° C., 75° C., 76° C., 77° C., 78° C., 79° C.,80° C., 81° C., 82° C., 83° C., 84° C., 85° C., 86° C., 87° C., 88° C.,89° C., 90° C., 91° C., 92° C., 93° C., 94° C., 95° C., 96° C., 97° C.,98° C., 99° C., or 100° C.

The electrolyte solution of the methods described herein, whether as anelectrolyte solution bath or spray, is heated to a higher temperaturethan electrolyte solutions of conventional anodizing methods. Inconventional anodizing methods, electrolyte solutions are typicallyheated to less than 60° C., for example, about 55° C. The methodsdescribed herein include a higher temperature electrolyte to moreefficiently form an anodized film layer on a surface of the metallicsubstrate. This further increases the overall efficiency of theprocessing by reducing the expense of carrying out the method.

Post-Treatment

After anodizing, the metallic substrate may undergo one or morepost-treatment steps. The post-treatment step may prepare the anodizedsubstrate for further processing.

Optionally, after the anodizing step, the surface of the metallicsubstrate may be rinsed with a solvent. The rinsing step may remove anyresidual electrolyte remaining after the anodizing step. Suitablesolvents include, for example, aqueous solvents (e.g., deionized water),organic solvents, inorganic solvents, pH-specific solvents (e.g.,solvents that do not react with the electrolyte), any suitable solvent,or any combination thereof. The rinse can be performed using sprays orby immersion. The solvent can be circulated to remove the residualelectrolyte from the aluminum alloy continuous coil surface and toprevent its resettling on the surface. The temperature of the rinsesolvent can be any suitable temperature.

Optionally, after the anodizing step and/or the rinsing step, thesurface of the metallic surface may be dried. The drying step removesany electrolyte solution and/or rinsing solvent deionized water) fromthe surface of the coil. In addition, the drying step may increasecorrosion resistance and/or adhesion performance of the thin anodizedfilm.

The drying step can be performed using, for example, compressed air, anair dryer, an infrared dryer, or any other suitable dryer. For airdrying the surface of the metallic substrate, e.g., with compressed air,the air may be heated to a temperature from 450° C. to 550° C., e.g.,from 460° C. to 530° C., from 465° C. to 515° C., from 470° C. to 500°C., or from 475° C. to 495° C. In terms of lower limits, the air, e.g.,compressed air, may be heated to a temperature greater than 450° C.,e.g., greater than 460° C., greater than 465° C., greater than 470° C.,or greater than 475° C. In terms of upper limits, the air, e.g.,compressed air, may be heated to a temperature less than 550° C., e.g.,less than 530° C., less than 515° C., less than 500° C., or less than495° C. For example, the surface of the metallic substrate may be driedwith air heated to a temperature of about 470° C., about 471° C., about472° C., about 473° C., about 474° C., about 475° C., about 476° C.,about 477° C., about 478° C., about 479° C., about 480° C., about 481°C., about 482° C., about 483° C., about 484° C., about 485° C., about486° C., about 487° C., about 488° C., about 489° C., about 490° C.,about 491° C., about 492° C., about 493° C., about 494° C., or about495° C.

The drying step can be performed for a time period of up to 5 minutes.For example, the drying step can be performed for 5 seconds or more, 10seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds ormore, 30 seconds or more, 35 seconds or more, 40 seconds or more, 45seconds or more, 50 seconds or more, 55 seconds or more, 60 seconds ormore, 65 seconds or more, 90 seconds or more, two minutes or more, threeminutes or more, four minutes or more, or five minutes.

After anodizing, the anodized substrate may be heat treated andprocessed to a desired condition or temper. For example, the anodizedsubstrate may be processed to achieve a T1 temper, a T2 temper, a T3temper, a T4 temper, a T5 temper, a T6 temper, a T7 temper, a T8xtemper, or a T9 temper.

System

The present disclosure also provides systems of making an anodizedsubstrate. In some non-limiting examples, the systems are configured toform an anodized film layer on at least one surface of a metallicsubstrate, e.g., a first surface of the metallic substrate. The firstsurface may be a top surface, a bottom surface, or a side surface of ametallic substrate, e.g., a continuous coil prepared in a horizontalprocessing line. In some cases, the first surface may be a frontsurface, a rear surface, or a side surface of a metallic substrateprepared in a vertical processing line. In some aspects, the systemsdescribed herein are configured to form the anodized film layer on afirst side of the metallic substrate and a second side of the substrate.For example, the anodized film layer can be formed on the top surfaceand the bottom surface of the metallic substrate (e.g., in thehorizontal processing line), and/or on the front surface and the rearsurface of the metallic substrate (e.g., in the vertical processingline). In further examples, the anodized film layer can be formed on theentirety of the metallic substrate (e.g., any exposed surface of thecontinuous coil).

The systems of making an anodized substrate, as described herein, may bea component of a larger processing system. For example, the systems canbe positioned downstream of a cold rolling mill, an annealing furnace, acontinuous annealing and solution heat treating (CASH) line, or anysuitable final processing equipment. Said another way, the system foranodizing the metal substrate described herein may be positioned betweena penultimate metal processing equipment and a metal coiler. Thus, themetallic substrate can be processed into a metal product and can beanodized immediately after processing without coiling the metal product(e.g., to provide the continuous coil). Accordingly, when the systemsdescribed above are placed in service in a metal processing line,parameters of the systems can depend on a line speed of the metalprocessing line, for example, line speeds selected and/or dictated byprocesses including the homogenization, the solution heat treating,and/or the annealing (i.e., temporally-dependent thermal processes).Thus, system parameters including applied power, electrolyteconcentration, electrolyte temperature, and/or dwell time, among others,can be tailored according to the predetermined/selected line speed ofthe metal processing line.

Electrolytic Cell

The systems described herein include an electrolytic cell (e.g., abipolar cell). In some cases, a single electrolytic cell is utilized ina processing line to form the anodized film layer in situ. In somecases, a plurality of electrolytic cells can be employed in a processingline. Employing a plurality of electrolytic cells in the processing line(e.g., continuous coil processing line) provides a customizableanodizing system. In some examples, an electrolytic cell can be used toelectrolytically clean the metallic substrate. In some cases, theplurality of electrolytic cells can be used to clean the continuous coiland form the thin anodized film on the continuous coil.

The electrolytic cell includes a metallic cathode. The metallic cathodeis an electrode from which the current employed to anodize the metallicsubstrate flows. The composition of the metallic cathode is notparticularly limited, and conventional cathode materials may be used.Exemplary cathode materials include steel, stainless steel, graphite,titanium, lead, and aluminum alloys. In some cases, the metallic cathodemay be a contact roll electrode.

The electrolytic cell may also include a counter electrode. The counterelectrode (also called the auxiliary electrode) is an electrode thatsupports the function of the metallic cathode, e.g., to increase therate of anodizing. One or more counter electrodes may form a circuitwith the metallic cathode when the system is energized. The one or morecounter electrodes may be mounted above the surface of the metallicsubstrate, below the surface of the metallic substrate, or above andbelow the surface of the metallic substrate, depending on desiredanodization. The composition of the counter electrode is notparticularly limited, and conventional auxiliary electrode materials maybe used. Exemplary counter electrode include steel, stainless steel,graphite, titanium, silver, and platinum.

Electrolyte Solution Source

The systems described herein also include an electrolyte solutionsource. The electrolyte solution source provides the electrolytesolution through which the electric current formed during anodizingflows. As noted above, the electrolyte solution is composed of anaqueous solution of an electrolyte, e.g., an electrolyte dissolvedand/or diluted in water. Suitable electrolytes include, for example,inorganic acids such as phosphoric acid, nitric acid, sulfuric acid,phosphoric acid, and combinations of these. Other exemplary electrolytesinclude aqueous solutions of sodium nitrate, sodium chloride, potassiumnitrate, magnesium chloride, sodium acetate, copper sulfate, potassiumchloride, magnesium nitrate, potassium nitrate, calcium chloride,lithium chloride, sodium carbonate, potassium carbonate, calciumcarbonate, sodium bicarbonate, ammonium acetate, silver nitrate, ferricchloride, ammonium pentaborate, boric acid, citric acid, ammoniumadipate, ammonium phosphate monobasic, or any combination thereof, amongothers. The electrolyte solution source is preferably composed of amaterial that is not negatively affected, e.g., corroded by theexemplary electrolyte solutions.

In some cases, the electrolyte solution source includes a tank, e.g., toform an electrolyte solution bath. During anodizing, the metallicsubstrate may be immersed in the electrolyte solution bath. The tank mayalso include an agitator for creating movement within the electrolytesolution bath and for dissipating heat produced during anodization. Theagitator may be a conventional agitator known to those in the art. Forexample, the agitator may be an inlet (e.g., a PVC pipe) for condensedair. In some cases, the electrolyte solution source includes one or morenozzles, e.g., for spraying the electrolyte solution onto a surface ofthe metallic substrate.

Support

The systems described herein also include one or more supports. Thesupport feeds and/or suspends the metallic substrate in the electrolyticcell. In some cases, the support immerses the metallic substrate in theelectrolyte solution bath. The composition of the support is notparticularly limited, and conventional cathode materials may be used.Exemplary cathode materials include steel, stainless steel, graphite,titanium, and aluminum alloys.

In some cases, the support includes one or more rollers for conveyingthe metallic substrate through the electrolytic cell. For example, thesupport may include a system of squeegee and/or contact rollers. In somecase, the support is a rack that suspends the metallic substrate in theelectrolyte solution bath.

Power Source

The systems described herein also include a power source. The powersource is capable of providing an AC and/or a DC to the electrolyticcell. Where the power source provides AC, the power source can form anAC circuit of any waveform, e.g., a sinusoidal waveform, a rectangularwaveform, a sawtooth waveform, a triangular waveform, or a squarewaveform.

Exemplary Configurations

In one non-limiting example of the system, a metallic substrate is fedinto the electrolytic cell by squeegee rollers positioned at an entranceto the electrolytic cell. The squeegee rollers can remove any residualsolvent remaining from a preparatory cleaning step. The electrolyte forthe anodization process is supplied to the surface of the metallicsubstrate by nozzles disposed above a first side of the metallicsubstrate and below a second side of the metallic substrate. Coatedstainless steel rollers positioned at a midpoint (or other suitableposition) in the electrolytic cell stabilize the metallic substrate andcontinue feeding the metallic substrate through the electrolytic cell.The electrolytic cell, including a first graphite counter electrode anda second graphite counter electrode that are powered by an alternatingcurrent (AC) source, supplies current to pass through the electrolyteand anodize the surface of the metallic substrate. Squeegee rollerspositioned at an exit of the electrolytic cell can remove residualelectrolyte and continue feeding the metallic substrate out of theelectrolytic cell.

In another non-limiting example, a contact roll is used as an electrodeto form the circuit to anodize a metallic substrate. The metallicsubstrate is fed to a contact roll electrode. The electrolyte foranodization is supplied to the surface of the metallic substrate bynozzles disposed above a first side of the metallic substrate and belowa second side of the metallic substrate. In a first configuration, thecontact roll electrode and a first counter electrode are configured toform a circuit and are powered by a current source configured to supplyan AC to pass through the electrolyte and anodize the surface of themetallic substrate. In a second configuration, the contact rollelectrode is an anode and the current source is configured to supply aDC to pass through the electrolyte and anodize the surface of themetallic substrate. Squeegee rollers are positioned downstream of thecontact roil electrode to remove any residual cleaner solvent from apreparatory cleaning step and continue feeding the metallic substratethrough the electrolytic cell, and squeegee rollers are positioneddownstream of the first counter electrode to remove residual electrolyteand continue feeding the metallic substrate to any further downstreamprocessing.

In another non-limiting example, a metallic substrate is placed inside arack constructed of titanium and secured to an aluminum bar. The rackimmerses the metallic substrate in an electrolyte solution bath within atank. Stainless steel cathodes are used to supply both AC current and DCcurrent received from a pulse reverse power supply through theelectrolyte solution bath to anodize one or more surfaces of themetallic substrate. Compressed air is supplied at the bottom theelectrolyte solution bath to agitate the electrolyte solution and removelocalized heat produced during anodizing.

Use of Anodized Substrate

The anodized substrates made according to the methods described hereincan be used in producing products, including products for use in, amongothers, automotive, electronics, and transportation applications, suchas commercial vehicle, aircraft, or railway applications. The continuouscoils and methods described herein provide products with surfaceproperties desired in various applications. The products describedherein can have high strength, high deformability (elongation, stamping,shaping, formability, bendability, or hot formability), and/or highresistance to corrosion. Employing a thin anodized film as a surfacepretreatment for a continuous coil provides a product that is deformablewithout damaging the pretreatment. For example, certain polymer basedpretreatment films can break during the bending operations used to forman aluminum alloy product.

In certain aspects, the anodized substrates can be coated, e.g.,Zn-phosphated and electrocoated (E-coated). The anodized substratesdisplay an improved adhesion of coatings as compared to continuous coilsthat do not contain an anodized film layer.

In some further aspects, the anodized substrates display a high level ofadhesion of laminates or lacquer films onto the surface of thecontinuous coils. Additionally, laminates and lacquers can be curedafter application at temperatures of up to about 230° C. The anodizedsubstrates are not damaged by elevated temperatures used in certaindownstream processing of aluminum alloy products, providing a thermallyresistant pretreatment for aluminum alloy products.

In some further aspects, the anodized substrates display excellent bonddurability.

In some examples, the anodized substrates can be used for chassis,cross-member, and intra-chassis components (encompassing, but notlimited to, all components between the two C channels in a commercialvehicle chassis) to gain strength, serving as a full or partialreplacement of high-strength steels. In certain examples, the anodizedsubstrates can be used in O, F, T4, T6, or T8x tempers. In certainaspects, the anodized substrates can be used to prepare motor vehiclebody part products, e.g., automobile body parts, such as bumpers, sidebeams, roof beams, cross beams, pillar reinforcements (e.g., A-pillars,B-pillars, and C-pillars), inner panels, side panels, floor panels,tunnels, structure panels, reinforcement panels, inner hoods, or trunklid panels. The disclosed anodized substrates can also be used inaircraft or railway vehicle applications, to prepare, for example,external and internal panels.

In some examples, the anodized substrates can also be used to preparehousings for electronic devices, including mobile phones and tabletcomputers. For example, the anodized substrates can be used to preparehousings for the outer casing of mobile phones (e.g., smart phones) andtablet bottom chassis. Exemplary consumer electronic products includemobile phones, audio devices, video devices, cameras, laptop computers,desktop computers, tablet computers, televisions, displays, householdappliances, video playback and recording devices, and the like.Exemplary consumer electronic product parts include outer housings(e.g., facades) and inner pieces for the consumer electronic products.

In certain aspects, the anodized substrates can further be used toprepare electronic device substrates. For example, an electronic devicesubstrate can include a conductive layer (e.g., an aluminum alloysubstrate, such as a continuous coil) and a dielectric layer (e.g., ananodized film layer) for preparing a layer-by-layer (e.g.,sandwich-style) electronic device. In some examples, the anodized filmlayer is configured to provide semiconductive properties to the aluminumalloy substrate. Semiconductive properties can include a tunable and/ortailorable conductivity of a material. In certain cases, theconductivity of a metallic substrate, e.g., a metallic substratecomposed of an aluminum alloy, can be decreased by forming an anodizedfilm layer thereon. In some examples, the anodized film layer can renderthe metallic substrate non-conductive (e.g., an insulator). For example,while the aluminum alloy is inherently conductive, the anodized filmlayer deposited onto the aluminum alloy substrate, including Al₂O₃, is anon-conductive and/or high-dielectric (i.e., high-k) film. The anodizedfilm layer can be deposited on at least a portion of at least onesurface of the aluminum alloy substrate. In some cases, an entiresurface of the metallic substrate can include the anodized film layer.For example, the anodized film layer can be rationally patterned on thesurface of an aluminum alloy substrate to define an electronic devicearea. In some examples, the anodized film layer can have any shapesuitable for providing an electronic device substrate, or the metallicsubstrate can be cut to any suitable shape to provide the electronicdevice substrate.

In certain aspects, the anodized film layer has a uniform thicknessacross the surface of the metallic substrate. The dielectric propertiesof thin films (e.g., anodized film layers) can be dependent on theparameters of the thin film. For example, the dielectric properties canbe proportional to the surface area of the device and/or the devicesubstrate and inversely proportional to the thin film thickness. Thus,providing a stable and uniform electronic device substrate requiresproviding a uniform anodized film layer. Additionally, the anodized filmlayer conforms to the surface morphology (e.g., surface roughness)further providing the uniform thickness across the area of theelectronic device and/or the electronic device substrate. The dielectricproperties of the anodized film layer are inversely proportional to thethickness. Thus, thinner portions of the thin anodized film canexperience dielectric breakdown and/or film damage when an electricfield and/or electric current is applied.

In some examples, the anodized film layer has a uniform dielectricconstant (k) across the area of the aluminum alloy. In certain aspects,the anodized film layer has a breakdown voltage of at least about ±10volts (V) (e.g., at least about ±11 V, at least about ±12 V, at leastabout ±13 V, at least about ±14 V, at least about 15 V, at least about±16 V, or at least about ±17 V). A breakdown voltage is a voltage atwhich, when applied to an electronic device having the thin anodizedfilm described herein, the dielectric properties of the anodized filmlayer are overcome by the applied voltage and electric current can flowacross the dielectric layer (e.g., the anodized film layer). Forexample, a capacitor includes two conductive electrodes having adielectric layer disposed between the electrodes. When a voltage isapplied to the capacitor, electrons accumulate on one electrode untilthe electric field is strong enough to drive the electrons across thedielectric layer, discharging the capacitor. Thus, when a capacitordischarges, dielectric breakdown occurs in the dielectric layer.

In further examples, the anodized film layer is configured to minimize aleakage current in an electronic device. For example, the anodized filmlayer can have a leakage current of up to about ±100 nanoAmperes (nA)(e.g., up to 90 nA, up to 80 nA, up to 70 nA, up to 60 nA, up to 50 nA,up to 40 nA, up to 30 nA, up to 20 nA, up to 10 nA, up to 1 nA, up to 90picoAmperes (pA), up to 50 pA, or up to 1 pA). A leakage current is anamount of current that can propagate across the dielectric layer (e.g.,the thin anodized film) at applied voltages that are less than thebreakdown voltage. In some cases, device defects and/or other deviceirregularities can allow current to leak through the dielectric layer,indicated as a leakage current. The anodized film layers describedherein allow a negligible amount of current to leak through thedielectric layer.

In some cases, the anodized film layer is stable under an appliedfrequency of up to 100 megaHertz (MHz) (e.g., up to 90 MHz, up to 80MHz, up to 70 MHz, or up to 60 MHz). Thus, high frequency electricityapplied to the thin anodized film will not damage the anodized filmlayer when a device using the electronic device substrates describedherein are placed in service (e.g., when used as a capacitor in acircuit).

In some non-limiting examples, the electronic device substrate comprisesa substrate for an energy storage device, a substrate for an energyharvesting device, a substrate for an energy consuming device, or asubstrate for a circuit component. For example, the energy storagedevice can be a capacitor, a supercapacitor, a battery, and/or arechargeable battery. In some cases, the energy harvesting device can bea photovoltaic device. Further, the energy consuming device can be alight-emitting diode, an organic light-emitting diode, a memory module,an electro-audio device, and/or an electrochromic device. In furtherexamples, the circuit component can be a diode, a rectifying diode, aresistor, a transistor, a memristor, any suitable circuit component, orany combination thereof.

Illustrations

Illustration 1 is a method of making an anodized substrate, the methodcomprising: providing a metallic substrate; and anodizing a surface ofthe metallic substrate in an electrolyte solution at a temperature from60° C. to 100° C. to form an anodized film layer, wherein theelectrolyte solution comprises from 0.01 M to 1 M of an electrolyte.

Illustration 2 is the method of any preceding or subsequentillustration, wherein the electrolyte is an inorganic acid selected fromthe group consisting of phosphoric acid, nitric acid, sulfuric acid,phosphonic acid, and combinations thereof.

Illustration 3 is the method of any preceding or subsequentillustration, wherein the electrolyte solution comprises from 0.05 M to0.5 M electrolyte, and wherein the electrolyte is phosphoric acid.

Illustration 4 is the method of any preceding or subsequentillustration, wherein the anodizing comprises applying a direct current(DC) having a voltage from ±10 VDC to ±35 VDC and/or applying analternating current (AC) having a voltage from ±10 VAC to ±35 VAC to theelectrolyte solution for at least 5 seconds.

Illustration 5 is the method of any preceding or subsequentillustration, wherein the anodizing comprises applying the AC for atleast 5 seconds before and/or after applying the DC for at least 15seconds.

Illustration 6 is the method of any preceding or subsequentillustration, further comprising: cleaning the surface of the metallicsubstrate; and/or drying the surface of the metallic substrate.

Illustration 7 is the method of any preceding or subsequentillustration, wherein cleaning the surface of the metal substratecomprises rinsing the surface of the metallic substrate with a solvent.

Illustration 8 is the method of any preceding or subsequentillustration, wherein the metallic substrate is not etched beforeanodizing.

Illustration 9 is the method of any preceding or subsequentillustration, wherein the metallic substrate comprises an aluminumalloy.

Illustration 10 is a method of making an anodized substrate, the methodcomprising: providing a metallic substrate; anodizing a surface of themetallic substrate in an electrolyte solution by applying a directcurrent (DC) having a voltage from ±10 VDC to ±35 VDC and applying analternating current (AC) having a voltage from ±10 VAC to ±35 VAC to theelectrolyte solution for at least 5 seconds, wherein the electrolytesolution comprises from 0.01 M to 1 M of an electrolyte; and optionally,drying the surface of the metallic substrate.

Illustration 11 is the method of any preceding or subsequentillustration, wherein the electrolyte is an inorganic acid selected fromthe group consisting of phosphoric acid, nitric acid, sulfuric acid,phosphoric acid, and combinations thereof.

Illustration 12 is the method of any preceding or subsequentillustration, wherein the electrolyte solution comprises from 0.05 M to0.5 M electrolyte, and wherein the electrolyte is phosphoric acid.

Illustration 13 is the method of any preceding or subsequentillustration, wherein the anodizing comprises applying the AC for atleast 5 seconds before and/or after applying the DC for at least 15seconds.

Illustration 14 is the method of any preceding or subsequentillustration, wherein the electrolyte solution is heated to atemperature from 60° C. to 100° C.

Illustration 15 is the method of any preceding or subsequentillustration, further comprising: cleaning the surface of the metallicsubstrate; and/or drying the surface of the metallic substrate.

Illustration 16 is the method of any preceding or subsequentillustration, wherein cleaning the surface of the metal substratecomprises rinsing the surface of the metallic substrate with a solvent.

Illustration 17 is the method of any preceding or subsequentillustration, wherein the metallic substrate is not etched beforeanodizing.

Illustration 18 is the method of any preceding or subsequentillustration, wherein the metallic substrate comprises an aluminumalloy.

Illustration 19 is a system for anodizing a metallic substrate, thesystem comprising: an electrolytic cell having a metallic cathode; anelectrolyte solution source for providing an electrolyte solutioncomprising from 0.01 M to 1 M an electrolyte; a support for suspendingthe metallic substrate in the electrolyte solution; and a power supplyfrom providing a direct current (DC) and alternating current (AC) to theelectrolytic cell and through the electrolyte solution.

Illustration 20 is the system of any preceding or subsequentillustration, wherein the electrolyte solution comprises from 0.05 M to0.5 M electrolyte, and wherein the electrolyte is phosphoric acid.

Illustration 21 is the system of any preceding or subsequentillustration, wherein the electrolyte solution source comprises a tankhaving an agitator.

Illustration 22 is the system of any preceding or subsequentillustration, wherein the electrolytic cell further comprises one ormore compound electrodes.

EXAMPLES

The following examples will serve to further illustrate the presentinvention without, however, constituting any limitation thereof. On thecontrary, it is to be clearly understood that resort may be had tovarious embodiments, modifications, and equivalents thereof which, afterreading the description herein, may suggest themselves to those ofordinary skill in the art without departing from the spirit of theinvention.

Example 1: Bond Durability Testing

As noted above, the methods of anodizing metallic substrates describedherein produce anodized substrates that demonstrate excellent bonddurability. This example serves to illustrate the improvement of thebond durability of metallic substrates anodized according to the methodsdescribed herein relative to metallic substrates anodized according toconventional methods.

Several samples of an anodized 7xxx series aluminum alloy were preparedaccording to the methods described herein to test the properties of theanodized metallic substrate. Each of the samples tested is shown inTable 1. In some samples, a 7xxx series aluminum alloy at F temper wasanodized and subsequently heat treated to a T6 temper (485° C. for 5minutes, then 125° C. for 24 hours). In other samples, a 7xxx seriesaluminum alloy at T6 temper was anodized without subsequent heattreatment. In other samples, a 7xxx series aluminum alloy at T6 temperwas anodized and subsequently heat treated comparably to a T6 temper(485° C. for 5 minutes, then 125° C. for 24 hours),

As shown in Table 1, two comparative samples were also preparedaccording to conventional anodizing methods. In particular, a firstcomparative sample was prepared by a conventional, two-step phosphoricacid anodizing method, and a second comparative sample was prepared by aconventional sulfuric acid anodizing method.

TABLE 1 Anodizing Post- Sample ID Temper Preparation ElectrolyteSolution Electric Current Treatment Sample 1A T6 Solvent clean Aqueoussolution, 24 VAC, 10 s; Drying 0.1 M phosphoric 24 VDC, 10 s  acid, 85°C. Sample 1B T6 Solvent clean Aqueous solution, 24 VAC, 10 s; Drying;0.1 M phosphoric 24 VDC, 10 s  Heat treat acid, 85° C. (485° C./ 5 min,125° C. 24 hr) Sample 2  T6 Solvent clean Aqueous solution, 24 VAC, 10s; Drying 0.1 M phosphoric 24 VDC, 20 s  acid, 85° C. Sample 3A T6Solvent clean Aqueous solution, 24 VAC, 10 s; Drying 0.1 M phosphoric 24VDC, 30 s  acid, 85° C. Sample 3B T6 Solvent clean Aqueous solution, 24VAC, 10 s; Drying; 0.1 M phosphoric 24 VDC, 30 s  Heat treat acid, 85°C. (485° C./ 5 min, 125° C. 24 hr) Sample 4  T6 Solvent clean Aqueoussolution, 24 VAC, 10 s; Drying 0.1 M phosphoric 24 VDC, 40 s  acid, 85°C. Sample 5A T6 Solvent clean Aqueous solution, 12 VAC, 10 s; Drying 0.1M phosphoric  12 VDC, 240 s acid, 55° C. Sample 5B T6 Solvent cleanAqueous solution, 12 VAC, 10 s; Drying; 0.1 M phosphoric  12 VDC, 240 sHeat treat acid, 55° C. (485° C./ 5 min, 125° C. 24 hr) Sample 6  T6Solvent clean Aqueous solution, 12 VAC, 10 s; Drying 0.1 M phosphoric 12 VDC, 120 s acid, 55° C. Sample 7  F  Solvent clean Aqueous solution,12 VAC, 10 s; Drying; 0.1 M phosphoric  12 VDC, 120 s Heat treat acid,55° C. (485° C./ 5 min, 125° C. 24 hr) Sample 8  F  Solvent cleanAqueous solution, 24 VAC, 10 s; Drying; 0.1 M phosphoric 24 VDC, 20 s Heat treat acid, 85° C. (485° C./ 5 min, 125° C. 24 hr) Sample 9  F Solvent clean Aqueous solution, 12 VAC, 10 s;  Drying; 0.1 M phosphoric24 VDC, 120 s Heat treat acid, 55° C. (485° C./ 5 min, 125° C. 24 hr)Comp. 1 T6 Solvent clean; Aqueous solution, 26 VAC, 10 s  Acid rinse;Alkaline 2 M phosphoric drying degrease; acid, 55° C. Alkaline etch;Acid soak; Electrolytic etch Comp. 2 T6 Solvent clean; Aqueous solution,12 A/ft², 600 s Acid rinse, Alkaline etch; 1.6 M sulfuric drying Acidsoak; acid, 20° C. Electrolytic etch

The three samples of exemplary anodized substrates were subjected tobond durability testing. In this testing, a set of 6 lap joints/bonds ofeach sample were connected in sequence by bolts and positionedvertically in a 90% relative humidity (RH) humidity cabinet. Thetemperature was maintained at 50° C. A force load of 2.4 kN was appliedto the bond sequence. The bond durability test is a cyclic exposure testthat is conducted for up to 60 cycles. Each cycle lasts for 24 hours. Ineach cycle, the bonds are exposed in the humidity cabinet for 22 hours,then immersed in 5% NaCl for 15 minutes, and finally air-dried for 105minutes. Upon the breaking of three joints, the test is discontinued forthe particular set of joints and is indicated as a first failure. Forthis disclosure, the completion of 45 cycles without a first failureindicates that the set of joints passed the bond durability test.

The bond durability test results are shown below in Table 2. In Table 2,each of the joints are numbered 1 through 6, where joint 1 is the topjoint and joint 6 is the bottom joint when oriented vertically. Thenumber in the cells, except for “45” and “60,” indicates the number ofsuccessful cycles before a break. The number “45” in a cell indicatesthat the joints remained intact for 45 cycles. The number “60” in a cellindicates that the joints remained intact for 60 cycles. The results aresummarized in Table 2 below:

TABLE 2 Bond Durability Test Coupon Arrangement 1 6 Trial Sample Top 2 34 5 Bottom 1 Sample 1A 7 7 5 5 7 6 2 Sample 1B 53 46 53 45 53 50 3Sample 2 21 21 16 13 15 21 4 Sample 3A 7 7 6 5 6 7 5 Sample 3B 40 40 3940 34 29 6 Sample 4 10 8 9 10 10 6 7 Sample 5A 27 77 27 22 24 23 8Sample 5B 47 24 47 27 47 26 9 Sample 6 25 25 24 25 23 15 10 Sample 7 6060 60 60 60 60 11 Sample 8 60 60 60 60 60 60 12 Sample 9 60 60 60 60 6060 13 Comp. 1 25 25 25 14 24 15 14 Comp. 1 33 33 33 27 13 7 15 Comp. 145 45 45 45 45 37 16 Comp. 1 45 45 45 45 45 36 17 Comp. 1 45 45 45 45 4536 18 Comp. 1 45 45 45 45 45 20 19 Comp. 1 20 31 31 24 31 29 20 Comp. 2.16 16 16 14 15 10 21 Comp. 2 18 18 10 18 12 12 20 Comp. 2 22 22 22 20 1816

The exemplary anodized substrates which were anodized according to thepresent disclosure demonstrated excellent bond durability, surviving 60test cycles without failure. The comparative anodized substratesdemonstrated comparatively poorer bond durability.

1. A method of making an anodized substrate, the method comprising:providing a metallic substrate; and anodizing a surface of the metallicsubstrate in an electrolyte solution at a temperature from 60° C. to100° C. to form an anodized film layer, wherein the electrolyte solutioncomprises from 0.01 M to 1 M of an electrolyte.
 2. The method of claim1, wherein the electrolyte is an inorganic acid selected from the groupconsisting of phosphoric acid, nitric acid, sulfuric acid, phosphonicacid, and combinations thereof.
 3. The method of claim 1, wherein theelectrolyte solution comprises from 0.05 M to 0.5 M electrolyte, andwherein the electrolyte is phosphoric acid.
 4. The method of claim 1,wherein the anodizing comprises applying a direct current (DC) having avoltage from ±10 VDC to ±35 VDC and/or applying an alternating current(AC) having a voltage from ±10 VAC to ±35 VAC to the electrolytesolution for at least 5 seconds.
 5. The method of claim 4, wherein theanodizing comprises applying the AC for at least 5 seconds before and/orafter applying the DC for at least 15 seconds.
 6. The method of claim 1,further comprising: cleaning the surface of the metallic substrate;and/or drying the surface of the metallic substrate.
 7. The method ofclaim 6, wherein cleaning the surface of the metal substrate comprisesrinsing the surface of the metallic substrate with a solvent.
 8. Themethod of claim 1, wherein the metallic substrate is not etched beforeanodizing.
 9. The method of claim 1, wherein the metallic substratecomprises an aluminum alloy.
 10. A method of making an anodizedsubstrate, the method comprising: providing a metallic substrate;anodizing a surface of the metallic substrate in an electrolyte solutionby applying a direct current (DC) having a voltage from ±10 VDC to ±35VDC and applying an alternating current (AC) having a voltage from ±10VAC to ±35 VAC to the electrolyte solution for at least 5 seconds,wherein the electrolyte solution comprises from 0.01 M to 1 M of anelectrolyte; and optionally, drying the surface of the metallicsubstrate.
 11. The method of claim 10, wherein the electrolyte is aninorganic acid selected from the group consisting of phosphoric acid,nitric acid, sulfuric acid, phosphonic acid, and combinations thereof.12. The method of claim 10, wherein the electrolyte solution comprisesfrom 0.05 M to 0.5 M electrolyte, and wherein the electrolyte isphosphoric acid.
 13. The method of claim 10, wherein the anodizingcomprises applying the AC for at least 5 seconds before and/or afterapplying the DC for at least 15 seconds.
 14. The method of claim 10,wherein the electrolyte solution is heated to a temperature from 60° C.to 100° C.
 15. The method of claim 10, further comprising: cleaning thesurface of the metallic substrate; and/or drying the surface of themetallic substrate.
 16. The method of claim 15, wherein cleaning thesurface of the metal substrate comprises rinsing the surface of themetallic substrate with a solvent.
 17. The method of claim 10, whereinthe metallic substrate is not etched before anodizing.
 18. The method ofclaim 10, wherein the metallic substrate comprises an aluminum alloy.19. A system for anodizing a metallic substrate, the system comprising:an electrolytic cell having a metallic cathode; an electrolyte solutionsource for providing an electrolyte solution comprising from 0.01 M to 1M an electrolyte; a support for suspending the metallic substrate in theelectrolyte solution; and a power supply from providing a direct current(DC) and alternating current (AC) to the electrolytic cell and throughthe electrolyte solution.
 20. The system of claim 19, wherein theelectrolyte solution comprises from 0.05 M to 0.5 M electrolyte, andwherein the electrolyte is phosphoric acid.
 21. (canceled) 22.(canceled)